Insulating material



May 30, 1933. R. BURNS 1,911,803

INSULATING MATER IAL Filed Sept. 25. 1929 //v VENTOR FF BURNS I Patented May 30, 1933 UNITED STATES PATENT OFFICE ROBERT BURNS, OE BROOKLYN, NEW YORK, ASSIGNOR TO BELL TELEPHONE LABORA- TORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK INSULATING MATERIAL Application filed September 25, 1929. Serial No. 894,961.

This invention relates to insulating materials and particularly to insulating materials which permit the grouping together of a large number of terminals in a minimum amount of space.

In many instances, for example, in terminal' stri s such as the test strip disclosed by U. S. atent 1,423,930 granted to Bruce Friele on July 25,1922, it is desirable to group together a large number of terminals in a minimum amount of space. Under such conditions the material employed for supporting these terminals should possess good mechanical and insulating properties so that a maximum number of terminals may be mounted in a minimum amount of space. This material should also permit the soldering of the terminals which are embedded therein to suitable conducting wires without the material. being unduly affected by the. heat which accompanies such soldering operations. In general phenol plastics, for exam 1e, bakelite resins, have been found satis actory' but it is generally recognized that materials of spect to their arcing characteristics, that is, when an arc is once established between two electrodes mou' tedin a phenol plastic, due either to a mechanical opening of the gap between. the electrodes or to a flash-over caused by conducting dbris between the electrodes, the arc is maintained for a sufficient length of time so as to leave the material permanently1 conducting.

On the other and certain other compounds such as cellulose acetate possess nonarcing characteristics consequently an are which is once established between two electrodes mounted in such a compound is not maintained. Such compounds, however, due totheirlow'meltingpoints and poor mechanical properties cannot be used in place of the materials generally employed in the manufacture of terminal strips.

\ The terminal strip of the present invention comprises a combination of a plastic compound and a non-arcing material combined in such a way that only the advantageous ualitiesof each are utilized. In general t is is accomplished by applying a this class are weak in re' 7 thin layer of a non-arcing com ound such as cellulose acetate over a base 0 phenol plastic complound such as bakelite, the" bakelite giving t e necessary mechanical and insulating properties to the strip so that a maximum number of terminals may be mountedin a minimum amount of space. The bakelite base also permits the soldering of theterminals to suitable conducti n wires without the base being unduly a ected by the heat which accompanies such soldering operations. The thin layer of cellulose acetate prevents an are which has been established between two electrodes from being maintained. In accordance with the preferred form of this invention the strip is made by combining the compounds in a single molding operation. In another form the strip is made by molding the bakelite'base first and then adding the layer of cellulose acetate by a two strips may be molded separately and then joined together by any suitable means, for example, by screws or pins.

A clearer understanding of this invention may be had by reference to the accentpanying drawing which shows the invention in its preferred form. I

A suitable number of terminals 10 are arranged so as to form a number of horizontal and vertical; rows. A mass of; insulating material is then molded about the terminals to form a block 11 having shoulders 12, which serve to support the block 11 between the vertical stiles of a switchboard frame. This block of 'insu-l'atin material comprises a rear portion 13' pro erably of a phenol plastic compound such as bakelite and a front portion 14 of a non-arcing materialsuch as cellulose acetate.- The two portions 13 and 14 are preferablyjoined together in a single molding operation but it is to be understood that the bakelite portion may be The terminals 10 are exposed at the front of the block 11 so that an electrical contact second molding operation or the may be made between the tip of an operators plug and any one of such terminals. For the purpose of making itmore convenient to find any one of the terminals 10 with an operators plug, grooves 15 are cut in the face of the block 11 crossing the face of the terminals 10. In this way the operator at'ter locating the horizontal row in which the line terminal is located mayguide the testing plug along the proper one of the horizontal grooves 15 until the desired terminal has been located. The grooves 15, however, are of less depth than the thickness of the outer layer of cellulose acetate. The terminals 10 protrude beyond the rear of block 11 terminating in flat portions 16 to which the proper electrical connections may be made. The base 13 of the phenol plastio compound gives the necessary mechanical and insulating properties to the strip 11 so that a maximum number of terminals 10 may be mounted in a minimum amount of space. Tie phenol plastic base also permits the soldering of the terminals 10 to the conducting wires without the block 11 being unduly affected by the heat which accompanies such soldering operations. Since the depth of grooves 15 is less than the thickness of the front layer of cellulose acetate 14, an are which has been once established between any two of the terminals 10 is prevented from being maintained.

What is claimed is:

1. A terminal strip comprising a base portion of a phenol plastic compound and a surface portion of cellulose acetate molded integral therewith.

2. In a terminal strip a plurality of terminals, and means for holding said terminals in spaced relation, said means comprising a rear portion of a phenol plastic compound and a front portion of cellulose acetate.

3. In a terminal strip, a plurality of terminals, and a mounting for supporting said terminals in spaced relation, said mounting comprising a front portion of cellulose acetate and a. rear portion of a phenol plastic compound molded integral therewith.

4. In a terminal strip a plurality of terminals, and a mounting for supporting said terminals in spaced relation, in a plurality of horizontal rows, said mounting comprising a rear portion of a phenol plastic compound and a front portion of a non-arcing material molded integral therewith and having grooves cut in the face of said front portion and passing through the end of each terminal in each horizontal row, the thickness of said front portion being greater than the depth of said grooves.

5. In a terminal strip a plurality of terminals, and a mounting for supporting said terminals in spaced relation in a plurality said mounting comprisof a phenol plastic comof horizontal rows, ing a rear portion pound and a front portion of cellulose ace tate and having grooves cut in the face of said front portion and passing through the end of each terminal in each horizontal row, the thickness of said front portions being greater than the depth of said grooves.

In witness whereof, I hereunto subscribe my name this 24th day of September, 1929.

ROBERT BURNS. 

